Troubles due to electromagnetic interference (EMI) have increased with functional advancement and prevalent use of electric and electronic devices. Electromagnetic noises are roughly classified into conduction noises and radiation noises.
A conduction-noise eliminating method uses a noise filter or the like. A radiation-noise eliminating method uses a metal case for electromagnetically isolating a space, another radiation-noise eliminating method inserts a metal sheet between wiring boards, and a third radiation-noise eliminating method coats a cable with a metal foil. These methods are effective in electromagnetically shielding circuits and power source blocks. Those shielding members used by the above methods are opaque and hence are not suitable for shielding electromagnetic wave emitted from a front surface of a display, such as a CRT and a plasma display panel (PDP).
The plasma display panel includes, in combination, a glass panel provided with data electrodes and a fluorescent layer, and another glass panel provided with transparent electrodes. When the plasma display panel operates, the plasma display panel generates intense electromagnetic radiation and near-infrared rays and a large amount of heat.
Generally, a front sheet is disposed on a front surface of the plasma display panel to shield the electromagnetic wave. The front sheet must be capable of reducing electromagnetic radiation of frequencies of 30 MHz to 1 GHz by 30 dB or above
Near-infrared rays of wavelengths between 800 and 1,100 nm emitted from the front surface of the display may also cause other devices, such as VTRs, to malfunction. Therefore, radiation of the near-infrared rays must be suppressed as well as the radiation of the electromagnetic wave.
In order to make images displayed by the display clearly visible, lines forming a metal mesh of a front sheet for electromagnetic shielding must be invisible, meshes are arranged regularly and the front sheet must have proper transparency (visible-light transmitting characteristics, visible-light transmittance).
Generally, the plasma display panel is characterized by its large panel size. An electromagnetic shielding sheet for a 37-inch PDP is as large as 621 mm×831 mm, and an electromagnetic shielding sheet for a 42-inch PDP is as large as 983 mm×583 mm. Some electromagnetic shielding sheets have sizes greater than those. The boundary between a mesh part and a grounding frame of such a large electromagnetic shielding sheet are liable to be broken during each of processes for manufacturing the electromagnetic shielding sheet to for incorporating the electromagnetic shielding sheet into a display. Thus, such a large electromagnetic shielding sheet is very difficult to handle.